The invention is based on a method for establishing the driving direction of a vehicle with an electronic compass in accordance with the type of the main claim. In a known navigation apparatus (DE-PS No. 27 54 888) the driving direction of a vehicle is established with a two-axis-magnetometer, whose output signals are fed to a correction unit for compensating magnetic interference fields in the vehicle. This solution is based on the assumption that an interference field is present in the vehicle which is superimposed to a ground field which is more or less screened by the chassis of the motor vehicle depending on the alignment of the vehicle. Thereby, a polar frequency is obtained for the measuring values of the magnetometer on the X and Y axis in the vector diagram by turning the vehicle, whose center point is displaced from the coordinate system of axes with the vector of the interference field and which forms an ellipse by the proportional change of the signals, whose axis extend parallel to the measuring axis in the vector diagram. Due to the proportional change of the one output signal, an ellipse should be formed into a circle and due to the zero point displacement the circle should be transferred to the coordinate system of the axes. This is checked by a control step in that the corrected signals are lifted to a square and must form a constant value when added (circular equation).
The correcting magnitudes which were established by the control stage must be established by scanning tests which are extremely cumbersome and erroneous. Moreover, in this manner only timely constant interference fields can be taken into consideration. A further, substantial disadvantage of the known method consists in that only an axis parallel displacement from the zero point has to be taken into consideration for the elliptical polar frequency of the weakened ground field, whereas the reality such an elliptical polar frequency is turned by an angular magnitude also in the vector diagram. Since this turning is not picked up in the known measuring method, a considerable deviation is obtained between the established and the actual driving direction with such an electronic compass.